[Devel] [PATCH rh7 1/4] ms/lockdep: Add lockdep_assert_not_held()

[Konstantin Khorenko]

From: Shuah Khan <skhan at linuxfoundation.org>

Some kernel functions must be called without holding a specific lock.
Add lockdep_assert_not_held() to be used in these functions to detect
incorrect calls while holding a lock.

lockdep_assert_not_held() provides the opposite functionality of
lockdep_assert_held() which is used to assert calls that require
holding a specific lock.

Incorporates suggestions from Peter Zijlstra to avoid misfires when
lockdep_off() is employed.

The need for lockdep_assert_not_held() came up in a discussion on
ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples
of functions that can use lockdep_assert_not_held().

Signed-off-by: Shuah Khan <skhan at linuxfoundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/

(cherry picked from ms commit 3e31f94752e454bdd0ca4a1d046ee21f80c166c5)
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 include/linux/lockdep.h | 9 +++++++--
 kernel/lockdep.c        | 6 +++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 242f69bddecf..1aff47ff71fd 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -367,8 +367,12 @@ extern void lockdep_trace_alloc(gfp_t mask);
 
 #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
 
-#define lockdep_assert_held(l)	do {				\
-		WARN_ON(debug_locks && !lockdep_is_held(l));	\
+#define lockdep_assert_held(l)	do {					\
+		WARN_ON(debug_locks && lockdep_is_held(l) == 0);	\
+	} while (0)
+
+#define lockdep_assert_not_held(l)	do {				\
+		WARN_ON(debug_locks && lockdep_is_held(l) == 1);	\
 	} while (0)
 
 #define lockdep_assert_held_exclusive(l)	do {			\
@@ -435,6 +439,7 @@ struct lock_class_key { };
 #define lockdep_is_held_type(l, r)		(1)
 
 #define lockdep_assert_held(l)			do { (void)(l); } while (0)
+#define lockdep_assert_not_held(l)		do { (void)(l); } while (0)
 #define lockdep_assert_held_exclusive(l)	do { (void)(l); } while (0)
 #define lockdep_assert_held_read(l)		do { (void)(l); } while (0)
 #define lockdep_assert_held_once(l)		do { (void)(l); } while (0)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 856b3d37c965..cdb82f1ce49a 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3657,8 +3657,12 @@ int lock_is_held_type(struct lockdep_map *lock, int read)
 	unsigned long flags;
 	int ret = 0;
 
+	/*
+	 * Avoid false negative lockdep_assert_held() and
+	 * lockdep_assert_not_held().
+	 */
 	if (unlikely(current->lockdep_recursion))
-		return 1; /* avoid false negative lockdep_assert_held() */
+		return -1;
 
 	raw_local_irq_save(flags);
 	check_flags(flags);
-- 
2.24.3